1. Field of the Invention
The present invention relates to a semiconductor device, a method for making the same, and to an electronic device utilizing the semiconductor device.
2. Description of the Related Art
In recent years, various wire-bond-type chip size packages (CSPs) have appeared in response to multi-electrode trends of semiconductor chips. Among the different types of CSPs, FIG. 7A shows a flexible printed circuit (FPC) type CPS. The FPC type CPS comprises a base a composed of a polyimide resin, and wiring films b composed of a metal such as copper formed on the surface of the base a. Holes c for forming electrodes (herein after referred to as “electrode-forming holes c”) are formed in the base a, and fine spherical electrodes d composed of solder are formed in the electrode-forming holes c. A semiconductor chip f placed on the base a is bonded to the base a with a silver-paste film e. Gold bonding wires g connect electrodes of the semiconductor chip f with the corresponding wiring films b. The semiconductor chip f and the bonding wires g are sealed with a sealing resin h.
FIG. 7B shows a rigid substrate type CPS. The rigid substrate type CPS comprises a rigid wiring substrate i having holes (through-holes) j for forming electrodes (hereinafter referred to as electrode-forming holes), wiring films k formed on the rigid wiring substrate i, and wiring films l. The wiring films l are connected to the wiring films k, functions as an external electrode, and does not require solder spherical electrodes. A semiconductor chip f is placed on an insulating film m composed of a resist between the wiring films k, and is bonded to the insulating film m with a silver-paste film e. Gold bonding wires g connect electrodes of the semiconductor chip f with the corresponding wiring films k. The semiconductor chip f and the bonding wires g are sealed with a sealing resin h.
Although the FPC type CPS shown in FIG. 7A has an advantage of a high rate of heat dissipation, it does not allow electroplating since fine solder spherical electrodes are in the wiring films b which are electrically isolated from each other. Thus, it is significantly difficult to form fine solder spheres. Since it is impossible to reduce the diameter of the electrode-forming holes c, reduction in the array pitch between the hole-electrodes is limited. Accordingly, the appearance of the electrode-forming holes and of the spherical electrodes is inferior. Since the wiring films b are formed by selective etching, production of a fine pattern is limited. Furthermore, the base a is flexible; hence workability is inferior and production of large devices is difficult.
Although the rigid substrate type has an advantage that no solder spherical electrode is formed, it is difficult to reduce the diameter of the electrode-forming holes to 0.35 mm or less. This is a factor limiting higher integration of semiconductor devices. Furthermore, production of a fine wiring film pattern is difficult, the appearance of the electrode-forming holes is inferior, and heat dissipation is slow. Since the electrode-forming holes are formed by drilling, production is difficult.